State Design Pattern in Python

"""
Allow an object to alter its behavior when its internal state changes.
The object will appear to change its class.
"""
import abc
class Context:
"""
Define the interface of interest to clients.
Maintain an instance of a ConcreteState subclass that defines the
current state.
"""
def __init__(self, state):
self._state = state
def request(self):
self._state.handle()
class State(metaclass=abc.ABCMeta):
"""
Define an interface for encapsulating the behavior associated with a
particular state of the Context.
"""
@abc.abstractmethod
def handle(self):
pass
class ConcreteStateA(State):
"""
Implement a behavior associated with a state of the Context.
"""
def handle(self):
pass
class ConcreteStateB(State):
"""
Implement a behavior associated with a state of the Context.
"""
def handle(self):
pass
def main():
concrete_state_a = ConcreteStateA()
context = Context(concrete_state_a)
context.request()
if __name__ == "__main__":
main()